Eighteen years ago, Bill Watterson pulled the plug on his incredibly popular “Calvin and Hobbes” comic strip, turned down millions of dollars in merchandising — and shut out a nation of loyal, hungry fans.

“That was when I was like, ‘Oh my God, one of your favorite things in life can die,’ ” says Colin Jorgensen, a Ridgewood, Queens, artist who goes by the pen name Cojo Art Juggernaut. “It was like losing a friend unexpectedly.”

The clever comic had elaborate art that far outclassed the scribbles of “Beetle Bailey.” Unlike “Bloom County,” it didn’t have an agenda; unlike “Family Circus,” it wasn’t squeaky clean. The content bounced between heavy chuckles, scenes of adult-defying imagination and the occasional dose of grim reality so heart wrenching that the colors on your funny page would be blotted with tears.

But this is a great year to be a “Calvin and Hobbes” fan: Not only did a new documentary, “Dear Mr. Watterson,” hit theaters Friday, but Watterson himself recently popped out of the shadows to give a rare interview to Mental Floss magazine. And book compilations of the comic strips have just become available on e-readers for the first time.

“Calvin and Hobbes” ran from 1985 to 1995, and is widely considered the last of the Golden Age of comics. The title characters were named for the theologian John Calvin and philosopher Thomas Hobbes. The six-year-old Calvin debated philosophy and psychology with Hobbes, a stuffed toy tiger who came to life — yet they also relished the joys of sledding, spacemen and a good cow-pie joke.

At its peak, the strip was carried in 2,400 newspapers around the world. But Watterson publicly battled with Universal Press Syndicate, which pushed him to turn the characters into a lucrative merchandising brand along the lines of “Garfield.”

When the final strip ran on Dec. 31, 1995, Watterson wrote in a letter to fans: “My interests have shifted however, and I believe I’ve done what I can do within the constraints of daily deadlines and small panels.”

Still, the magic of a boy and his imaginary friend never really left fans’ hearts. Eighteen compilation books of the strip have sold more than 45 million copies and remain perennial Amazon best sellers.

Creative fans have taken to YouTube, creating tribute art that shows Calvin and Hobbes as characters from TV shows such as “Firefly” and “Community”; one animation of Calvin’s famous snowmen battle scenes has been viewed 880,000 times.

Documentary director Joel Allen Schroeder chose not to go after Watterson for an interview, focusing instead on the illustrator’s impact on other artists and performers, including actor and “Robot Chicken” co-creator Seth Green, as well as cartoonists Bill Amend (“FoxTrot”) and Berkeley Breathed (“Bloom County”), as well as the widow of “Peanuts” creator Charles Schulz. “Calvin and Hobbes are the last great cartoon characters,” Breathed says in the film. Green talks about how he and his friends made Calvin shirts on their own because there was no official merchandise to buy.

Schroeder was comforted to learn that the image of Watterson as a hermit is incorrect: The artist seems to have a full life, with family, friends and hobbies. He lives outside Cleveland with his wife, Melissa.

“I think he’s just a normal guy who prefers to keep to himself out of the spotlight,” Schroeder says.

Tellingly, the Mental Floss interview touches on why Watterson hasn’t done a follow-up to “Calvin and Hobbes”: He’s intimidated by his own success.

“ ‘Calvin and Hobbes’ created a level of attention and expectation that I don’t know how to process,” he tells the magazine.

In a rare treat for fans, Watterson, now 55, will take part in a March 2014 art show at Ohio State University in Columbus. It’s unclear whether he will display new original work.

Nevin Martell, author of the 2010 book “Looking for Calvin and Hobbes,” was unsuccessful in his attempts to track down Watterson. But if Watterson called him tomorrow and agreed to talk, Martell knows what he would ask.

“I just want to know if he’s had enough space from ‘Calvin and Hobbes,’ and all the angst and clearly bitter elements,” he says, “that he can just sit back and appreciate all the joy that his readers take from his strip.”